func renderToScreen() {
gl.BindFramebuffer(gl.FRAMEBUFFER, 0)
gl.Viewport(0, 0, winWidth, winHeight)
gl.UseProgram(shaderTextureDisplay.glProg)
gl.BindTexture(gl.TEXTURE_2D, rttFrameTex)
gl.Uniform1i(shaderTextureDisplay.unifTex, 0)
gl.BindBuffer(gl.ARRAY_BUFFER, dispVertBuf)
gl.EnableVertexAttribArray(shaderTextureDisplay.attrPos)
gl.VertexAttribPointer(shaderTextureDisplay.attrPos, 3, gl.FLOAT, gl.FALSE, 0, gl.Pointer(nil))
gl.DrawArrays(gl.TRIANGLE_FAN, 0, 4)
gl.DisableVertexAttribArray(shaderTextureDisplay.attrPos)
gl.BindBuffer(gl.ARRAY_BUFFER, 0)
}
func renderToTexture() {
gl.BindFramebuffer(gl.FRAMEBUFFER, rttFrameBuf)
gl.Viewport(0, 0, texWidth, texHeight)
gl.ClearColor(0.1, 0.2, 0.3, 1)
gl.Clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT)
gl.UseProgram(shaderTextureCreator.glProg)
gl.BindTexture(gl.TEXTURE_3D, volTex)
gl.Uniform1i(shaderTextureCreator.unifTex, 0)
gl.BindBuffer(gl.ARRAY_BUFFER, rttVertBuf)
gl.EnableVertexAttribArray(shaderTextureCreator.attrPos)
gl.VertexAttribPointer(shaderTextureCreator.attrPos, 2, gl.FLOAT, gl.FALSE, 0, gl.Pointer(nil))
gl.DrawArrays(gl.TRIANGLE_FAN, 0, 4)
gl.DisableVertexAttribArray(shaderTextureCreator.attrPos)
gl.BindBuffer(gl.ARRAY_BUFFER, 0)
}